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Voltmeter Working Principle Introduction
Nov 01, 2017

The voltmeter is an instrument that measures the voltage, and the common voltmeter - voltmeter symbol is "V". The conventional pointer voltmeter includes a sensitive galvanometer with a permanent magnet inside the potentiometer, a series of wires formed by wires between the two terminals of the galvanometer. The coil is placed in the magnetic field of the permanent magnet and Through the transmission device connected with the table pointer. Most of the voltmeter is divided into two ranges. The voltage meter has three terminals, a negative terminal, two positive terminals, the positive pole of the voltmeter is connected with the positive pole of the circuit, and the negative pole is connected with the negative pole of the circuit.

The traditional pointer voltmeter and ammeter are based on a principle that is the magnetic effect of the current. The greater the current, the greater the magnetic force generated, the voltmeter is the greater the swing on the watch, the voltmeter has a magnet and a wire coil, through the current, the coil will produce a magnetic field, coil power In the role of the magnet will be deflected, which is the ammeter, voltmeter head part.

As the voltmeter to be measured in parallel with the measured resistance, so if the direct current meter with a voltmeter, the current is too large, will burn the meter, then the need to voltage in the internal circuit in series a large resistance , So after the transformation, when the voltmeter and then in parallel in the circuit, due to the role of resistance, the voltage applied to both ends of the meter most of the voltage is shared by the series resistance, so the current through the meter is actually very small, so Can be used normally.

DC voltmeter symbols to V under a "_", AC voltmeter symbols to V plus a wave line "~".

The voltmeter is a large resistor, ideally considered to be open. In parallel circuit in parallel with the voltmeter (in parallel with other appliances) and electrical appliances, if there is no other electrical appliances in the trunk, can be considered to measure the power supply voltage (because the parallel circuit on the use of all the power supply voltage ); If the trunk is also connected to other electrical appliances, then the electricity to share part of the power supply voltage, that voltage meter can only measure part of the voltage (which is connected with the electrical appliances which voltage).

To know that in the voltmeter, there is a magnet and a wire coil, through the current, the coil will produce a magnetic field, so the coil power after the role of the magnet will rotate, which is the ammeter, voltmeter head part.

This meter can pass the current is very small, both ends can withstand the voltage is very small (certainly far less than 1V, may only zero and a few volts or even smaller), in order to measure the actual circuit voltage, The voltmeter in series with a relatively large resistance, made of voltage meter. In this way, even if the two ends with a relatively large voltage, but most of the voltage is applied to the increase in the large resistance on the meter on the voltage will be very small. The voltmeter is a very large internal resistance of the instrument, generally should be greater than a few thousand euros. The head is made by the effect of the magnetic field by the conducting conductor in the magnetic field. There is a permanent magnet inside the pole, a magnetic field is generated between the poles, a coil in the magnetic field, a spring of the spring at both ends of the coil, and a terminal of the spring connecting table. A spring is connected between the spring and the coil, At the front of the ammeter, there is a pointer. When there is current through, the current along the spring, the shaft through the magnetic field, the current cut magnetic induction line, so the role of magnetic field force, so that the coil deflection, driving the shaft, the pointer deflection. As the size of the magnetic field increases with the current increases, so you can observe the degree of deflection of the pointer to see the size of the current.